Optical analyzers utilizing attenuated total internal reflection are disclosed in my earlier U.S. Pat. No. 3,460,893, Issued Aug. 12, 1969 for APPARATUS FOR ANALYZING A CONTINUOUS MOVING STRIP BY MEANS OF ATTENUATED TOTAL REFLECTION, my United Kingdom Patent No. GB 2,105,058B, Patent published Jan. 8, 1986 entitled FRUSTRATED MULTIPLE TOTAL INTERNAL REFLECTION ABSORPTION SPECTROPHOTOMETER, and my U.S. Pat. No. 5,185,640, Issued Feb. 9, 1993 entitled MULTIFACETED PROBES FOR OPTICAL ANALYSIS which patents are incorporated herein by reference. Each of the above patents discloses internal reflection rods for optical analysis. In the British Patent and the latter United States Patent the rods are utilized for analyzing fluids, particularly liquids.
All of these elements and all of the similar elements utilized in the prior art, I believe, have required the use of optical elements, such as lenses or reflecting mirrors to concentrate light from a light source into the elements and to collect the light exiting the elements and direct it to a detector.
Such light concentrating and light collecting optical elements add to the cost of any analyzer using totally internally reflecting rods according to the prior art.
A need exists in the beverage dispensing industry for an inexpensive monitor of the carbon dioxide (CO.sub.2) content of carbonated water, for example, as supplied to the multiple soft drink dispensers used in restaurants and bars. The variation in CO.sub.2 content is one of the main causes of improper taste in soft drinks.